*THE HULL TRUTH is the world's largest FREE network for the discussion of Boating & Fishing. Whether you're researching a new boat, or are a seasoned Captain, you'll find The Hull Truth Boating & Fishing Message Forum contains a wealth of information from Boaters and Sportfishermen around the world.

I'm considering purchasing a 38'Mediterranean Sportfish & have the choice of either a 92 with 300hp. Cats with 1600hrs. or one with 210hp Cummins w/1100hrs. Speed is not an issue with me but dependability & repairability are my major concerns as I plan on using this boat for fairly long range trips. Thanks for any info offered.

From everything I have ever heard, the 3116 is by far the worst engine cat ever made. Pascoe's website (I think www.yachtsurvey.com)? goes into great detail about thier shortcomings. I think I would go with the Cummins.

1. It does not have an aftercooler. Less maintenance because you don't have to clean it and you don't have to worry about it (the aftercooler) failing. An aftercooler that fails leaks saltwater into the engine and if not found immediately will result in the engine having to be overhauled. Major $$$$.

2. The cummins is an easier block to find in a shortblock configuration and therefore much more affordable to overhaul when and if the time ever comes.

just be sure you can live with the cruise speed of having 90 less hp if you choose to go that way.

The cat 3116 did have their problems and cat addressed them with upgrades. With any purchase of diesels I would have a cat certified tech. or cummins certified tech. survey the engines. You can take this with a grain of salt,but people usually talk about the bad experiences, hardly ever the good ones.

From a resale standpoint the Cat motor will be better. The problems with the early 3116's have been corrected and if the engines have run for 1600 hours then that is evidence. However 1600 hours is close to the life expectancy for either of those motors in recreational use. Both are very lightly built motors which were designed as a low cost alternative to gas. The Cummuins is far cheaper to replace, but I do not see significant differences in reliabilty.
My biggest concern would be the Cummins will work a lot harder than the Cat to push the boat. 210 HP is really not enough for that hull. I sold one with 300 Cummins and that was about right. Cruised at 20 Knts. That boat had 1500 hrs on it and one engine failed within 3 months of purchase. Good news is that a Cummins long block, remanufactured fron Cummins is less than $10 grand.

Marine Diesel question – I’ve never owned a boat with diesels, but I’ve spent the better part of my life around large diesel powered farm machinery and construction equipment. I am curios to know why the “engine life” for CAT and Cummings marine diesels is considered so much shorter then others. For example, farm tractors and bulldozers etc, generally run to 8-10K hours before a rebuild. Granted they don’t normally run in the potentially corrosive salt water environment, but then marine diesels aren’t subject to the dust, dirt, and heavy lugging loads that construction and agricultural diesels are operated in either. I would venture to guess that the maintenance intervals are the same – daily checks, 100 hour oil changes, sequential/multiple fuel, oil, and air filters etc.

m3taco: I'm told many boat engines are overloaded from the get-go, or become overloaded as weight is added to the boat, or marine growth and bottom paint, etc. By overloaded I mean the boat cannot reach the rpms it is rated for. For example, I believe the Cats and Cummins >300 hp are rated for 2800 rpms at wot. Perhaps they only reach 2700 rpms at wot. If you look at an engine/prop demand curve, a 2700 rpm wot motor will produce more horsepower at every point along the curve than it was designed for, producing more heat, and creating little room for error.

Also, marine engines have high hp/displacement ratios. Think of a dragster which goes through a rebuild every hour? or so. Marine engines aren't quite a dragster, but the engine is producing a lot of horsepower compared to a non-turbo version. For example, I have a 4 cylinder Yanmar with 3.6 liter displacement producing 170 horsepower. In the non-turboed version of my engine, I believe the same displacement produces 110 hp, while the highest hp version is 240 hp. The 110 hp engine is simply not stressed as much. I believe most industrial/commercial applications are these lower-hp/displacement units, and they can be run close to wot continuously and run forever.

Although most boaters would be better served to put in low hp/displacement engines, at about $60 per hp or so it is expensive to put in a low-stress power unit. Besides, many of us put on fewer than 125 hours a year so that if the engine only lasts 2500 hours it may be time for a modern power plant anyway.

Its a great question and one asked quite often. The engines in the farm equipment/over the road trucks etc don't put out the hp (with the same block) that the "high performance" marine engines put out....

for example a 3406E truck engine has a max rating of 600 hp....the same engine in the marine configuration is 800 hp. The engine life is based on fuel consumption therefore the 800 hp engine (basically under load all the time) won't live as long as the 600 hp version (that gets to go "downhill too) if both run hard....

With heavy equipment the weight is not a factor so you can put a heavier duty engine in with little consequence....in a planing boat, especially with todays performance expectations, weight is everything.....more hp, less weight is what everyone is going for (buying).

I have a 38' Med with 250 HP detroit diesels, and cruise at about 19-20 knots at 2800 RPM.
I think that with 210 HP, you will be lucky to get 17-18 knots. These are 25,000 lb boats.
Just something to be aware of.